This invention relates to a cutting apparatus. More particularly this invention concerns an apparatus for severing an elongated web workpiece of sheet material such as floor covering linoleum, needle felt, elastomeric or synthetic-resin sheeting, textile material, or the like.
A severing device of the above-described general type is known built along the principle of a radial-arm saw, that is having a circular blade which engages in a slot of a support surface on which the material to be cut is held or displaced. This blade is driven at relatively high speed, often of the order of several thousand rpm, so that while cutting the blade does not exert any force tending to displace the workpiece on the support surface. With such an arrangement the blade can be drawn across the workpiece, or the blade can be held stationary and the workpiece pulled along under the blade.
Such a machine is relatively expensive and has the considerable disadvantage that when used with many workpieces, as for instance synthetic resins, the rapidly rotating blade heats up and damages the workpiece. In particular when cutting thermoplastic synthetic-resin material it is necessary frequently to shut down the machine and clean the blade to remove from it hardened-on synthetic-resin material which was melted onto the blade during the cutting operation.
It is also known to provide an apparatus, such as shown in U.S. Pat. No. 3,296,911 with a non-driven blade having a sharpened edge. Such an arrangement is invariably provided with a hold-down device in order to retain the workpiece flat on the table underneath the blade. The disadvantage of this system is that the hold-down device itself exerts on the workpiece a force tending to displace it on the support surface and wrinkle it. Furthermore the non-driven and usually non-rotating blade also exerts considerable force in the plane of the workpiece tending also to displace it along the table so that the cut is not exactly in the desired position. With a blade of this type, that is not driven, the cutting edge must be maintained extremely sharp in order to obtain a satisfactory cut.
It has also been suggested, as for instance in U.S. Pat. No. 3,137,192 to hold the workpiece down against the cutting surface by means of rollers biased by a spring downwardly against the support surface. Extending through a slot in the table of this device is a sharpened blade which makes the cut. Such an arrangement is disadvantageous in that, first of all, the blade must once again be maintained extremely sharp in order to obtain a clean cut. When dull the device must be taken apart so that that small area of the blade that does all of the cutting can be resharpened. What is more if a relatively thick workpiece is used the downwardly effective biasing spring is compressed to a greater extent so that the downward biasing force increases. Thus the biasing force bears a direct relationship to the workpiece thickness, which once again is undesirable in many instances.
Yet another arrangement is seen in U.S. Pat. No. 3,766,816 which has a paper cutter wherein a hold-down bar is laid on top of the workpiece to be cut adjacent a squared-off cutting edge. A combined wheel/cutter is rolled along the edge of the table, with the wheel rolling on the hold-down bar and the cutter engaging past the edge of the table. With this arrangement the provision of a hold-down bar makes the device completely unusable in an arrangement where the workpiece must be pulled past the blade, and further increases the cost of the assembly. The use of a hold-down strip is particularly bothersome in installations wherein considerable productivity is desired, as it must be painstakingly positioned before each cut and then removed after the cut is made.